Process of distilling crude petroleum and product thereof



EDGAR M. CLARK, or NEW YORK, Y., Assmnon 'ro STANDARD OIL COMPANY, OF

NEW YORK, N. Y., A CORPORATION OF NEW JERSEY.

PROCESS OF DISTIIILING CRUDE PETROLEUM AND PRODUCT THEREOF.

No Drawing.

To all whom it may concern Be it known that I, EDGAR M. CLARK, a citizen of the United States. residing at New York, in the county of New York and State of New York, have invented a new and useful Improvement in Processesof Distilling v Crude Petroleum and Product Thereof, of

which the following is a specification.

The present invention is directed to certain improvements in the art of distilling crude petroleum oil and will be fully understood from the following specification: In'

order to obtain from crude petroleum oil a maximum yield of valuable products, it is in general required that the oil be distilled to the point of dryness, that is, until the residue of distillation is petroleum coke. Ofi'setting the higher yield of valuable products obtained in this fashion however, there are attendant disadvantages well-known to those skilled in the art, which disadvantages become more and more serious as the specific gravity of the crude oil increases. Thus, in a case of the ordinary quality of Mexican crude petroleum now produced and having a Baum gravity of from 21 to 23, there isobtaineda coke residue veryhigh in sulphur and amounting to as much as l-t to 18% of the weight of the crude distilled with an accompanying gas loss of 2 to 5%. Under many conditions. this coke residue mayv be worth less than the cost of removing it from the stills. A typical process of running Mexican crude petroleum to coke may be represented substantially as follows:

Yields. s Naphtha 14% Refined oil 10% Gas oil or high-grade fuel oil- 56% Coke and gas 20% It will "be understood, of course, that the 56% gas oil or high-grade fuel oil fraction will usually be subjected to further refining operations for the recovery of paraffin waxand the separation of high-viscosity frac-- tions suitable for lubricants, the extent to which such further refining is carried being dependent upon the quality of the oil, the equipment of the refinery and the demand for the highly refined products. Under the most favorable conditions, however, the loss in coke and gas together with the expense of maintaining the refinery equipment and re- Specification of Letters Patent. Patented Apr. 18, 1922. Application filed March 31, 1919. Serial No. 28%,262.

moving the coke from the stills renders this method of running so unattractive that many of the larger refiners prefer to merely fsklm the ordinary grade of Mexican crude petroleum, that is, distill off only about 15% which is less than the total content of naphtha and refined oil .-marketing the whole of the 85% residue as a low-grade fuel oil, which must compete with coal as a bunker fuel for ships. Aside from the waste of the valuable lubricant fractions and wax of the crude oil inherent in the use of this skimming process. there is a further disadvantageous result of considerable economic importance.

at a profit, from any ordinary grade of gas oil or fuel oil. a considerable quantity of gasoline. and this process which has come into wide use throughout. the United States has measurably added to the gasoline supply. The reduced Mexican crude, however, that is the low grade fuel oil produced by skimming Mexican crude oil. does not constitute a satisfactory raw material for treatment according to the Burton cracking process referred to, or according to any other cracking process which has yet come into wide use. One reason for this unsatisfactory operation of the cracking process referred to, is that the accumulation of carbon in the cracking stills is so rapid that the amount of gasoline which can be produced before cleaning is'required is cut to a very small figure.

By the present invention there isprovided a method of obtaining from crude oil, and particularly from heavy asphaltic base crudes. such as the Mexican, a maximum yield of valuable products including heavy hydrocarbons suitable for use as a charging stock in cracking stills, without encountering any of the difiiculties met with in the heretofore known process of running such crude down to coke. 'In brief, it may be said that my present process contemplates arrestin the distillation at the point where the cru e oil is reduced to a high-melting point pitch, and then fiuxing this pitch with a quantity of fuel oil suflicientto produce a product fluid at ordinary temperatures and capable of being marketed as a liquid fuel product. The preferred process in accordance with my present invention, and as applied to Mexican crude petroleum, may be described as follows:

The apparatus for conducting the process consists of a string of continuous stills, for example, twelve stills arranged to constitute a continuous battery with provisions for feeding the first still of the string and causing the oil to overflow from each still into the next succeeding still, each still having vapor pipes and condenser equipment, all according to common practice. Each still will, furthermore, be provided with the usual means for introducing open steam (i. e., directly injecting steam), so that the distillation may .be conducted with fire and steam. The last still of the string will, furthermore, be equipped with means for introducing the fluxing oil into the end at which the pitch residue enters, the draw-off being at the opposite end as in ordinary practice.

In addition to the ordinary continuous still equipment described in the foregoing, it is desirable that the plant in which my process is carried out be likewise equippedwith an adequate number of pressure cracking stills, such as are described in the patent to Burton referred to.

In the handling of the oil according to the method of the present invention, and with the equipment described, the crude oil is continuously pumped into the first still of the series, is there subjected to the heating effect of the still furnace, supplemented by the continuous injection of stea (preferably "superheated steam) into the oil body, distills off its lighter component-s, overflows to the next still in the series, and is thus subjected to distillation at increasing temperatures successively in its course through the battery of stills. The distillation will be conducted at such a rate that approximately 75% of the total volume of the crude will have been distilled off before the residue reaches the last still of the string. It will, in general, be unnecessary to fire this last still. The

25% residue of the Mexican crude petroleum will be a pitch of very high melting point, for example, 192 F., but is a relatively mobile fluid at the temperature at which it enters the-fiuxing still. The process of disftillation being a continuous one, as described, there will be a continuous stream of this high-melting-point pitch flowing into the inlet end of the fluxing still, and

' simultaneously there will be pumped into the same end of the still, preferably in a heated condition, an approximately equal volume of the tar or residue resulting from the practice of the cracking process in the pres- Gravity 235 B.

Viscosity 49 at 100 F. (Saybolt). Pour Below zero. 'Flash 195 F.

The two streams, i. e. that of pressure tar and high-melting-point pitch enter the still continuously and simultaneously at one end, both being preferably at an elevated temperature as described, and traverse the length of the still, being Ineanwhilesubjected to continuous agitation by the superheated steam from the apertures in the submerged steam coils in the still. Under these conditions, the fluxing process proceeds satisfactorily and there is formed an intimate mix: ture of the two fluids with the. incidental re sult that lighter constituents of the pressure tar, should any be present, are'distilled off and pass to the condensers with the steam. The fluxed product flows out of the end of the still opposite that at which its constituents entered, and is pumped off to storage, preferably through heat exchangers, in the ordinary manner. This fluxed fuel producedas above described may have the following approximate specifications:

Gravity i 14.3 B. Viscosity- 870 at 212 F. (Saybolt). Pour 65 F. Flash 290 F.

As will appear from the foregoing specifications, it constitutes a petroleum product sufficiently mobile to be marketable as a liquid fuel, that is, it is capable of being handled as a fluid under ordinary atmospheric conditions, requiring the use of only.

The continuous distillation of the Mexican crude petroleum in the manner above described therefore gives approximately the following yields of distilled products:

Naphtha L- 14% Refined oil; 10%

Gas and fuel oil (including high viscosity oils and wax) 50% Liquid fuel constituent 25% Gas 1% According to the equipment of the refinery, the quality of the oil and demand'for the refined products, the 50% gas or fuel oil cut from the crude, or any part't-hereof, may

be re-run for the separation of high-viscosity lubricants and other highly refined heavy oils, or pressed for the recovery of :Wax, or

both. In any event, the wholeof this 50% fraction of the Mexican crude oil is marketable as a gas oil-or fuel oil of good quality, constituting as it does a distillate and not a reduced crude product.

I prefer to employ either the whole of this intermediate fraction of the Mexicancrude or that portion remaining after the wax and lubricants are extracted, as a charging stock for the production of gasoline by a pressure distillation process, such as that of Burton referred to. In such a pressure distillation process I may. for example, charge into the pressure still 12,000 gallons of the intermediate fraction of the Mexican crude, and as a result of the cracking operation conducted itself a suitable material for re-running in I the pressure stills for ,theproduction of a further quantity of gasoline, it requires redistillation to put it in good condition for such re-running in the pressure stills, and, furthermore, the chemical changes which it has undergone in the still render it less desirable as a charging stock for the pressure stills than is a fresh distillate from crude oil. On the other hand, while the pressure tar is not so desirable as a fresh charging stock for the pressure stills,'itis a .particularlvadvantageous fluxing agent by reason of its relatively low cold test and viscosity.

The general scheme of operation of the preferred distilling process, according to the present invention. is therefore as follows:

. 100 barrels of Mexican crude is distilled with fire and steam in a continuous distillatory apparatus as described, to produce of distillate and 25% of high-melting-point pitch residue. heavier distillate, for example. 50 barrels is used as a charging stock for pressure stills, being subjected to the cracking treatment for the production of gasoline andyielding approximately 50%, or 25 barrels of gasoline,

with a residue of 25 barrels of pressure tar. This pressure tar is used for fluxing off the 25 barrels of high-melting-point pitch residue to give .50 barrels of low-grade liquid fuel.

approximate gross yield from 100 barrels of Mexican crude would be 40 barrels naphtha and refined oil, 10 barrels paralfin wax and lubricants and 50 barrels bunker fuel, dis- A large proportion of the In the example given therefore the yield of the most val liable products; that is,

naphtha andarefined oil, wax and lubricants, without carrying the distillation down to coke, ither in the original distillation of the crude oil or in the re-distillation of pressure tar. All of the disadvantages which follow from carrying the distillation to coke are thus avoided.-all of .the advantages'of continuous distillationcwith steam are obtained, the pressurestill equipment of the refinery is assured ofan adequate supply of high-grade charging stock suitable for conversion into gasoline, and an advantageous means of disposing of the pressure tar without further treatment thereof is offered.

In th treatment of higher grade crude oils, such as mid-continent crude oil which mately 15% in the first eight stills of the series. The last four stills are used in successlon in the following manner:

The streamof 15% bottom is run into one of these stills (previously empty) up to the capacity of the still, when it is shut off or diverted to another empty still. The full still is now fired, and steam blown in in the usual manner until there has been produced, for example, 10% of-slop distillate high in crystalline wax and lubricants and, perhaps, 157 of still wax distillate if the latter is desired. There will then remain in the still a high-melting-point pitch. representing about-1%, for example, of the crude oil. This pitch will now be fluxed with an approximately equal quantity of a residual or by-product petroleum hydrocarbon of the grade of 51, fuel oil, such, for example, as the pressure-tar heretofore that is poor in wax and high viscosityfractions. and when the fluxing operation has -referred to, or other heavy oil. of low grade,

been completed by the use of the steam jets for agitation,- thefluxed product, consitutinga low grade liquid fuel oil suitable for use as a bunker fuel, will be drawn out... The still will now be empt and ready for use in its turn for conducting the final distillation operation and fluxing upon a fresh charge of bottoms from the continuous stills.

While I have in the foregoing described in considerable detail the preferred process in accordance with my invention and have indicated some variants thereof, it will be understood that this is illustrative only and that my invention is not to be regarded as limited to the particular procedure described, except in so far as such limitations may be included within the accompanyinggclaims in which it is my intention to claim all novelty inherent in the invention asfbroadly as is permissible in view of the prior art.

hat I claim is:

1. The method of distilling petroleum oils which consists in reducing the oil by continued distillation toa residuum of the consistency of a high melt-point pitch and mixing directly with the residuum while in heated, mobile state a heavy petroleum oil of low viscosityto produce a material capable of being handled as a fluid at atmospheric temperatures.

2. The method of distilling crude petroleum oil which consists in reducing the oil by continued distillation with open steam to a residuum of the consistency of a high melt-point pitch and mixing directly with the residuum while in heated, mobile state a heavy petroleum oil of low viscosity to 3. The improvement in the art of distill ing crude oil which consists in continuing the distillation until the oil under treatment has been reduced to the consistency of a high melting point pitch, adding to said pitch a heavy petroleum oil of low viscosity and cold test and removing from the mixture and condensing the lighter vapors, a mixed fuel capable of being handled as a liquid at ordinary atmospheric temperatures being thereby produced.

4:. The improvement in the art of distilling crude oil which consists in continuing the distillation until the oil under treatment is reduced to the consistency of a high melting point pitch, adding to said pitch heavy fiuid residues from the cracking of petroleum oil, removing from the mixture and condensing the lighter vapors,a mixed fuel capable of being handled as a liquid at ordinary atmospheric temperatures being thereby produced.

5. The method of refining crude petroleum which consists in subjecting the oil to distillation until it has been reduced to the consistency of a high-inelting-point pitch, treating the heavier portion of the distillate by a cracking operation yielding light oils and a heavy residue, and fiuxing the said pitchby the additionthereto of the heavy residue of cracking.

6. The method of refining crude petroleum which consists in subjecting the oil to rated heavy distillate by a cracking operation yielding light oils and a heavy residue, and fluxing the said pitch by the addition thereto of the heavy residue of cracking.

7. The method of refining crude petroleum which consists in subjecting the oil to continuous distillation with fire and steam until it has been reduced to the consistency of a high-melting-point pitch, treating the heavier portions of the distillate. by a cracking operation yielding light oils and a heavy residue, and continuously fiuxing the said pitch by the additon thereto of the heavy residue of cracking.

8. The method of refining crude petroleum which consists in subjecting the oil to continuous distillation With fire and steam until it has been reduced to the consistency of a high-melting-point pitch, separating the lubricating fractions and wax from the distillate, treating the separated heavy distillate by a cracking operation yielding light oils and a heavy residue, and continuously 'fiuxing the said pitch by the addition thereto of the heavy residue of cracking.

9. The method of refining heavy asphaltic base crude petroleum, such as Mexican high-melting-point petroleum pitch fluxed with a heavy distillate substantially free of lubricating fractions and crystalline wax,

- 11. A petroleum fuel product capable of being handled as a fluid and comprising the bottom of Mexican crude petroleum reduced to about 25% by distillation with fire and steam, fluxed with a heavy distillate of the character of pressure tar.

EDGAR M. CLARK. 

